It is well established that malodour may be caused by a number of compounds, such as volatile sulphur compounds (VSC), nitrogen containing compounds, short fatty acids etc.
Volatile Sulphur Compounds (VSC)
Bad Breath: Malodour in the form of a bad breath emanating from the oral cavity is typically a consequence of volatile sulphur compounds (VSC). VSCs are produced by oral anaerobic Gram-positive bacteria by degradation of sulphur containing proteinaceous substrates in the salvia. The VSCs are released into the oral environment where they are mixed with air expired from the lungs resulting in a unpleasant odour coming out of the mouth. The above mentioned proteinaceous substrates may be owing to the intake of foods, such as meat, fish, spices, vegetables, dairy products etc. Volatile Sulphur Compounds such as for instance diallyl sulfide, (a thioether) can be found in e.g. garlic being well known for causing a repellent bad breath.
Burned flavour: When heat treating certain foods, such as UHT-treating milk, a "burned" flavour caused by Volatile Sulphide Compounds may arise.
Examples of VSCs are hydrogen sulfide (H.sub.2 S), dimethyl sulfide (CH.sub.3 SCH.sub.3), diallyl sulfide, and the one being regarded as the most potent methyl mercaptan (CH.sub.3 SH) also called methanethiol.
Nitrogen Containing Compounds
Nitrogen containing compound such as ammonia, indole, skatole and a number of amines are also well-known to give a bad smell. An amine such as trimethylamine gives a fishy smell.
Diapers and the like: A source of nitrogen containing compounds are urine, faeces and blood giving a bad smell known by most people from either soiled diapers or other hygiene products, such as adult incontinence products, training pants, feminine napkins, tampons and the like.
The bad smell coming from diapers and the like is typically a consequence of growth of bacteria, especially Escherichia coli, Enterococcus faecalis and Proteus mirabilis, present on the skin in the perineum (the region between the anus and the external sexual organs). All strains of Proteus form the enzyme urease during their metabolism. Urease has the ability to rapidly break down urea (constituting about 2% of human urine) into ammonia causing an unpleasant odour.
Short Fatty Acids
Short fatty acids, such as butyric acid (C4), are also known to give a malodour. After having worn shoes for a whole long warm day most people know the bad smell of perspiring feet caused by the short fatty acids such as butyric acid.
Further, clothes washed with a laundry detergent comprising a lipase sometimes have an unattractive odour resembling the odour of spit-up from babies. This malodour is believed to arise when the lipase degradation product of triglyceride containing soils on the fabric is not completely removed during the wash or rinse cycle. Said degradation product consists of short free fatty acids (e.g. butyric acid).
Proteinaceous Substrates
Proteinaceous substrates such as amino acids, peptides, proteins and mixtures thereof may be substrates in odor formation. Especially the sulfur-containing group of amino acids (cysteine, cystine and methionine) are major odor contributors. The main odoriferous products produced from these substrates are hydrogen sulfide and methyl mercaptan. However tryptophan, ornithine and other amino acids are also known to be contributors to odor formation.
Removal or Reduction of Malodour
A number of odour controlling agent and systems have been described in the literature. For instance, carbon is e.g. in the form of activated carbon well-known for its ability to adsorb odoriferous molecules.
U.S. Pat. No. 5,593,398 discloses protective underwear with malodorous flatus filter comprising activated carbon as the malodour controlling agent
Zeolitic materials have been shown to be effective against malodour associated with body fluids.
JP patent application no. 02068117 relates to deodorising means e.g. for diapers containing zeolite, copper and activated charcoal.
U.S. Pat. No. 4,026,814 concerns a soap with a reduced tendency to generate malodours during storage. The soap comprises an enzyme system which contains an oxido-reductase enzyme such as alcohol dehydrogenase and/or aldehyde dehydrogenase, and a hydrogen acceptor selected from the group of nicotinamide-adenine-dinucleotide and/or nicotinamide-adenine-dinucleotide phosphate.
JP patent application no. 9038183 (Takasago Perfumery CO Ltd.) concerns a deodorant composition capable of removing the smell of bad breath, refrigerator, pets etc. The composition comprise of phenolic compounds and an enzyme which oxidise phenolic compounds. As preferred phenolic compounds the following diphenolic compounds are mentioned: cathecol, catechin compounds, tyrosine and chlorogenic acid. Tyrosinase, peroxidase, glucose oxidase, and laccase are mentioned as the oxidative enzyme. Preferred enzymes are of mushroom belonging to Agrinus bisporus var. albidus and Boletus pulverulentus or of fruit origin, such as apple, pear (gobou).
U.S. Pat. No. 3,903,259 concerns a method of deodorising diapers and human excreta comprising applying to the diapers or the excreta a chemical composition which in its simplest form consists of an acidic material, an antibiotic material, and a solvent. The impregnating composition may also contain a chelating agent and a wetting agent. The treatment of diapers results in a marked decrease in offensive odours from excreta, thus making the changing of sorted diapers less unpleasant.
U.S. Pat. No. 3,935,862 discloses a disposable diaper comprising means for inhibiting ammonia formation therein including an aminopolycarboxylic acid compound in an amount of at least 0.001 gm. per square inch.
U.S. Pat. No. 4,385,632 concerns a germicidal absorbent body for collecting blood, faeces and urine which contains a water-soluble copper salt which impedes bacterial growth, prevents the breaking down of urea into ammonia and complex-binds ammonia so as to prevent the occurrence of unpleasant odour.
U.S. Pat. No. 4,551,187 describes a deodorant body cleansing composition in the form of a liquid or solid opaque bar, comprising a detergent and a specific carbohydrate capable of reducing the odour-causing bacterial population on the body (skin and/or hair), without the use of anti-microbials. The essential deodorant agent which is a group of carbohydrates specifically effective against the odour-causing bacteria on the skin and/or hair, are mannose, glucose, and oligomers thereof, i.e. dimers, trimers, and tetramers.
U.S. Pat. No. 5,395,555 concerns an aqueous cleaning composition for carpets, rugs, and textiles particularly useful in reducing malodour of urine stains. The composition comprising a) from about 4.23% to about 4.28% by weight of a sodium or potassium salt of a diethylenetriaminepentaacetic acid, an ethylenediaminetetraacetic acid, a N-hydroxyethylethylenediaminetriacetic acid, or mixtures thereof; b) from about 1.95% to about 2.05% by weight of a diethylenetriaminepentaacetic acid, an ethylenediaminetetraacetic acid, a N-hydroxyethylethylenediaminetriacetic acid, or a mixture thereof; C) from about 0.82% to 0.98% of a sodium lauryl sulfate; d) from about 0.49% to 0.59% by weight of an acrylate copolymer of the formula CF.sub.3 (CF.sub.2)n CH.sub.2 OCOC(CH.sub.3).dbd.CH.sub.2 wherein n is from 6 to 8; e) from about 0.22% to about 0.27% by weight of an octylphenoxy-polyethoxy ethanol; f) from about 0.35% to about 0.5% by weight of fragrance; and g) from about 0.00003% to about 0.05% by weight of a preservative 1,2-benzoisothiazole-3(2H)-ones.